A particulate filter for collecting particulates contained in exhaust gas discharged from an engine is known. The filter has a honeycomb structure formed of porous material. Further, the filter has a plurality of passages, some of them being closed at their upstream end by plugs, and remaining of them being closed at their downstream end by plugs. In this filter, the exhaust gas passes through partitions defining the passages, and thereafter flows out of the filter.
In this type of the filter, as the exhaust gas flows out of the filter after passing through the partitions, the filter has a high particulate collection ratio. However, the passages of the filter are closed by the plugs, and therefore, the productivity of the filter is low and the cost for producing the filter is high.
Further, as shown in FIG. 3A, as the exhaust gas hits against the plugs, the exhaust gas does not flow smoothly into the passages of the filter. In addition, when the exhaust gas flows near the upstream plugs, the exhaust gas flows with turbulence, and thus the exhaust gas does not flow smoothly into the passages of the filter. Further, as shown in FIG. 3B, when the exhaust gas flows near the downstream plugs, the exhaust gas flows with turbulence, and thus the exhaust gas does not flow smoothly out of the filter. For these reasons, the filter has a large pressure loss.
The purpose of the invention is to provide an exhaust gas purification device having a particulate filter having a small pressure loss.